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Geometry Question

Old 07-13-16, 03:04 PM
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8bits
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Geometry Question

Need some help about frame geometry from you guys.

I had a Cervelo T1 for 3 years and it served me well but an oportunity came up and I sold it.

I'm contemplating getting a Dolan DF4, however Dolan's geometry is so different from my T1 and my road bike, a BMC Race Machine that I'm kinda lost.

DF4's have a much shorter TT but a much much longer reach, the stack is also a lot shorter but I was expecting that since it's very low. I was pretty confortable using the T1, does that mean that the DF4 is not for me? What other framesets I should be looking at at this price point?

Here's the measurements:
The stack/reach/effective top tube length for the T1 is: 51/373/529
The stack/reach/effective top tube length for the BMC RM01 is: 53/378/535
The stack/reach/effective top tube length for the DF4 is: 477/392/515

Last edited by 8bits; 07-13-16 at 03:22 PM.
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Old 07-13-16, 03:18 PM
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gycho77
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Originally Posted by 8bits View Post
Need some help about frame geometry from you guys.

I had a Cervelo T1 for 3 years and it served me well but a oportunity came up and I sold it.

I'm contemplating getting a Dolan DF4, however Dolan's geometry is so different from my T1 and my road bike, a BMC Race Machine that I'm kinda lost.

DF4's have a much shorter TT but a much much longer reach, the stack is also a lot shorter but I was expecting that since it's very low. I was pretty confortable using the T1, does that mean that the DF4 is not for me? What other framesets I should be looking at at this price point?

Here's the measurements:
The stack/reach/effective top tube length for the T1 is: 51/373/529
The stack/reach/effective top tube length for the BMC RM01 is: 53/378/535
The stack/reach/effective top tube length for the DF4 is: 477/392/515
In this forum, you can find a link to track frames stack, and other information, but I cannot find the link right now. So if I find the link, I will edit this post and tell you.
Also you will be better off buying Affinity Kissena because of the stack.
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Old 07-13-16, 03:39 PM
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1incpa
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I found it Gycho,
Stack and reach link:
https://634818e2b81b8cf8095d4b4bd96e...GdKVk0/2d.html
Hope this helps.
PI
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Old 07-13-16, 03:56 PM
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8bits
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Originally Posted by gycho77 View Post
Also you will be better off buying Affinity Kissena because of the stack.
Couldn't find anywhere for stack and reach of the Kissena, not on their website nor the aforementioned chart
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Old 07-13-16, 06:30 PM
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You can see in the graph, but the T1 is the shortest and tallest of all the bikes I had data for. What stem length and angle were you using on the T1? And any spacers? If you're lucky, you may be able to get your bar stack and reach to match.
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Old 07-13-16, 08:23 PM
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So Affinity doesn't publish their geometry, but here are the geometry estimates for a couple ST angles. I've seen an old geo chart listing 74 as the st angle for all sizes. (here)

Model Brand Size TT Stack Reach ST Ang HT Ang HT Length ST Length
Affinity Kissena S/52 520 497 368 73 ? 145 520
Affinity Kissena S/52 520 500 377 74 ? 145 520
Affinity Kissena S/52 520 502 385 75 ? 145 520

But please do keep in mind that this is a calculation for stack and reach rather than an actual measurement. Also, the head tube length is pretty well correlated with the stack on most frames, and the Kissena's HT is actually taller than the T1. Which probably bodes well - it's certainly one of the taller frames around. I'd still want to try it first.
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Old 07-13-16, 08:48 PM
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Originally Posted by Hrothgar42 View Post
You can see in the graph, but the T1 is the shortest and tallest of all the bikes I had data for. What stem length and angle were you using on the T1? And any spacers? If you're lucky, you may be able to get your bar stack and reach to match.
I was using: 90mm stem with -6 deg., 2x10mm spacers and an Easton EC90 track handlebar which has 95 reach and 168 drop. This got me thinking, maybe if I change the handlebar for a Scatto that has less drop and less reach maybe it will fit me fine...
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Old 07-13-16, 10:41 PM
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Originally Posted by 8bits View Post
I was using: 90mm stem with -6 deg., 2x10mm spacers and an Easton EC90 track handlebar which has 95 reach and 168 drop. This got me thinking, maybe if I change the handlebar for a Scatto that has less drop and less reach maybe it will fit me fine...
I think this website could help you solve the problem
https://yojimg.net/bike/web_tools/stem.php
you could calculate this by using Heattube length(stem height section), but I am not sure it's going to be super accurate.
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Old 07-13-16, 10:43 PM
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8Bits,

If you really want to do this right, find a bike fitter with a proper fit bike. It doesn't have to be a fancy electronic one. An old Serotta mechanical beast is fine.

Get fit and determine the riding position that you'd like to use as your base position. Then get the detailed measurements and go hunting for the frames that are close.

The $100-$200 you spend one time on the fitting will be worth it because you probably won't be lucky enough that the next frame you buy on a hunch happens to be perfect for you.

An alternate way to do this is to take the frame that you are about to buy and send the dimensions to the fitter and have him plug in the numbers on the fit bike. You bring your favorite bars and then sit on it all and see how it feels.

But, I think the former way is better.

Take it from a guy who spent waaaaay too much money chasing the perfect frame.
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